The invention relates to a rapping assembly and electrode support means for electrostatic precipitators and more particularly relates to the rapping shaft drive means and rapping shaft supports for electrostatic precipitators wherein the rapping shafts and electrode support means are suspended from the roof of an electrostatic precipitator.
Electrostatic precipitators are provided with discharge and collecting electrodes which attract particulate matter from contaminated air streams passing through the precipitator. Particulate matter or dust which piles up on these electrodes must be removed by shaking or washing of these electrodes. Normally the shaking is accomplished by vibrators or rapping devices. The rapping devices usually include a rotating shaft with tumbling rappers affixed thereto, each of the rappers being disposed to strike a rapper receiving means attached to one or more carriers for discharge or collecting electrodes, the striking sending vibrations through the electrodes thereby dislodging dust accumulating thereon. These rotating rapping shafts are connected to high voltage electrical sources and in many instances extend through the sidewall of a precipitator housing and are electrically insulated with respect to the housing and the drive motor. This type of construction has the disadvantage in that the distance of the electrostatic precipitator from other electrically driven machines presents an unsafe condition as the drive motor for the rapping shaft projects outwardly from the vertically extending sidewalls of the precipitator housing. In U.S. Pat. No. 3,427,787 a device is described which includes a rapping shaft suspended from the roof of an electrostatic precipitator with the driving means for the rapping shaft being attached to the precipitator roof. However, the suspension of the discharge system and the drive of the rapping shaft requires at least three openings in the precipitator roof. It is noted that the opening for the driving rod for the rapping shaft is relatively large in order to avoid any electrical arc-overs. As a result, the insulator is placed in the dust-laden gas stream and during operation the insulator is susceptible to being covered with a layer of dust. Furthermore, during shutdown periods for the precipitator, the dust-layer on the insulator may become humid, thus increasing the danger of arc-overs when the high voltage is reapplied to the device. Also, the drive mechanism for the rapping shaft is a ratchet device which is disposed within the gas stream and is subjected to particulate build-up, the particulate build-up interfering with efficient operation of the ratchet device.